  
window.onload = function() {
    // 鼠标滚动事件
    document.onmousewheel = function(e) {     
        if (e.wheelDelta > 0) { //当滑轮向上滚动时
            if (window.pageYOffset > 2368 ) {
                // scrollTo(0,2368);
                window.scrollTo({ 
                top: 757*3, 
                behavior: "smooth" 
                });
            }
            else if(window.pageYOffset > 1971){
                // scrollTo(0,1611);
                window.scrollTo({ 
                top: 1514, 
                behavior: "smooth" 
                });
            }else if(window.pageYOffset > 1314){
                // scrollTo(0,856);
                window.scrollTo({ 
                top: 757, 
                behavior: "smooth" 
                });
            }else if(window.pageYOffset > 657){
                // scrollTo(0,0);
                window.scrollTo({ 
                top: 0, 
                behavior: "smooth" 
                });
            }
        }
        if (e.wheelDelta < 0) { //当滑轮向下滚动时
            if (window.pageYOffset  < 457) {
                // scrollTo(0,657);
                 
                window.scrollTo({ 
                top: 757, 
                behavior: "smooth" 
                });
                
            }else if(window.pageYOffset < 1271){
                  
                window.scrollTo({ 
                top: 1514, 
                behavior: "smooth" 
                });
                // scrollTo(0,1431);
            }else if(window.pageYOffset < 1728){
                // scrollTo(0,2168);
                window.scrollTo({ 
                top: 757*3, 
                behavior: "smooth" 
                });
            }
            
           
        }
    }


} 
